Prevalence of SCN1A-Related Dravet Syndrome among Children Reported with Seizures following Vaccination: A Population-Based Ten-Year Cohort Study

Objectives: To determine the prevalence of Dravet syndrome, an epileptic encephalopathy caused by SCN1A-mutations, often with seizure onset after vaccination, among infants reported with seizures following vaccination. To determine differences in characteristics of reported seizures after vaccination in children with and without SCN1A-related Dravet syndrome. Methods: Data were reviewed of 1,269 children with seizures following immunization in the first two years of life, reported to the safety surveillance system of the Dutch national immunization program between 1 January 1997 and 31 December 2006. Selective, prospective follow-up was performed of children with clinical characteristics compatible with a diagnosis of Dravet syndrome. Results: In 21.9 % (n = 279) of children, a diagnosis of Dravet syndrome could not be excluded based on available clinical data (median age at follow-up 16 months). Additional follow-up data were obtained in 83.9 % (n = 234) of these children (median age 8.5 years). 15 (1.2 % of 1,269; 95%CI:0.6 to 1.8%) children were diagnosed with SCN1A-related Dravet syndrome. Of all reported seizures following vaccinations in the first year of life, 2.5 % (95%CI:1.3 to 3.6%) were due to SCN1A-related Dravet syndrome, as were 5.9 % of reported seizures (95%CI:3.1 to 8.7%) after 2nd or 3rd DTP-IPV-Hib vaccination. Seizures in children with SCN1A-related Dravet syndrome occurred more often with a body temperatur